Tractor Mode Marine Propulsion

ABSTRACT

A drive for a marine vessel may include a fully wetted propeller with a fixed drive shaft configuring the propeller in a tractor mode wherein the propeller pulls the water rearwardly relative to a bow of the marine vessel when traveling in a forward direction. The propeller is preferably mounted in a range of 10% to 60% of a length of the marine vessel toward the how from a transom and operates cavitation-free.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The preferred embodiments relate to propulsion of marine vessels; and more particularly, propulsion of a marine vessel with a fully wetted, submerged propeller in a tractor mode configuration and powered by a fixed shaft.

2. Discussion of the Related Art

Marine vessels are commonly constructed with a propeller facing the rear end or transom in order to “push” it through the water. This is commonly referred to as “pusher configuration”. In a “puller configuration”, also referred to as “tractor configuration” or tractor mode, the propeller faces the bow of the vessel, such that the vessel is “pulled” through the water.

Tractor configurations are commonly known in the aircraft industry but have not made any significant entry into the marine space. Tractor configurations have been used in pod-style drives for large yachts, typically, 30 feet in length or longer, but are not offered for more traditional drive systems. Pod drives also come with high maintenance, high costs, and more complications than other drives. Due to these factors, pods are not implemented in smaller marine vessels. Pod drives also may extend the propeller lower in the water than other configurations increasing the opportunity to strike ground or other foreign bodies. Should such an impact occur, the damage can be catastrophic to the pod and incur significant costs or a total loss of the vessel.

Traditional drive systems, such as direct drive systems, are less complicated and have much lower manufacturing costs as well as lower maintenance costs. Such drive systems also do not extend deep into the water and conic with minimal repair costs should the propeller impact ground or another foreign object.

When using a more traditional drive system, such as an outboard or a direct drive, the marine industry installs propellers in a pusher configuration. This is done not only as a result of tradition, but simply because it works. However, many marine vessel designers also operate under the old belief that pusher configurations simply perform better than tractor configurations. In fact, in the POD space, it has been proven that the tractor configuration gives greater propulsive efficiency.

What is therefore needed is a marine propulsion design that can take advantage of a propeller disposed in a tractor configuration, while avoiding the high costs and maintenance of known tractor configurations, such as pod drives.

What is additionally needed is a marine propulsion system that can be used on all sizes of marine vessels, large and small. Furthermore, a marine propulsion system that can combine the benefits of a tractor configured propeller with a traditional drive system such as direct drive was also desired.

SUMMARY AND OBJECTS OF THE INVENTION

A marine vessel includes a hull with an underside. The underside may include a tunnel configured to accept a drive. A propeller may be mounted at least partially within the tunnel in a tractor mode configuration such that the propeller rotates to create a thrust that pulls the marine vessel in a forward direction.

The propeller may be fully submerged in water, also known as fully wetted, and does not produce vapor cavities when powering the marine vessel at a cruising speed (e.g., 20 knots or more) of up to 50 knots or more, resulting in a completely “clean” inflow condition. In fact, vapor cavities are avoided at speeds of 50 knots or more. The propeller may also include efficiency ratios of over 60% with an overall propulsive coefficient of over 50%. The propeller includes a diameter in the range of 50% to 90% of a diameter for lateral dimension) of the tunnel. The propeller rotates to produce a thrust disc such that both an upper half and a lower half of the propeller produces thrust without turbulent flow characterized by a vortex and cavitation.

The marine vessel may further include a shaft joined to the propeller with a shaft angle of about 6 degrees to a horizontal plane when the marine vessel is stationary in the water, producing an effective shaft angle of 0 degrees when the marine vessel is in motion at a cruising running angle of attack and does not produce cavitation during operation when powering the marine vessel at a speed of up to 50 knots or more.

The marine vessel may also include a fixed shaft for transferring power to the propeller. The fixed shaft may be mounted with a positive shaft angle producing lift in a bow region of the marine vessel when moving at cruising speed.

The marine vessel may further include a power source within the hull, rearward of the propeller or any desired placement in the hull that delivers power to the fixed shaft and propeller with an angled v-drive also mounted within the hull and rearward of the propeller. The propeller may also be mounted in a range of 10%-50% toward the bow from the transom of the marine vessel.

An interceptor may be affixed on a trailing edge of the tunnel or a transom of the marine vessel providing the bow with an adjustable positive and a negative lift when moving at cruising speed. Notably, the marine vessel also does not produce a rooster tail when cruising at up to 50 knots or more.

These and other aspects and objects of the present invention will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following description, while indicating preferred embodiments of the present invention, is given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the present invention without departing from the spirit thereof, and the invention includes all such modifications.

BRIEF DESCRIPTION OF THE DRAWINGS

A clear conception of the advantages and features constituting the present invention, and of the construction and operation of typical mechanisms provided with the present invention, will become more readily apparent by referring to the exemplary, and therefore non-limiting, embodiments illustrated in the drawings accompanying and forming a part of this specification, wherein like reference numerals designate the same elements in the several views, and in which:

FIG. 1 illustrates a perspective view of the bottom of a marine vessel according to the present invention;

FIG. 2 illustrates a partial cross sectional side view of a marine vessel showing the present invention according to FIGS. 1; and

FIG. 3 illustrates a close-up, partial cross sectional side view of a marine vessel showing the present invention according to another embodiment.

In describing the preferred embodiment of the invention which is illustrated in the drawings, specific terminology will be resorted to for the sake of clarity. However, it is not intended that the invention be limited, to the specific terms so selected and it is to be understood that each specific term includes all technical equivalents which operate in a similar manner to accomplish a similar purpose. For example, the words “connected”, “attached”, or terms similar thereto are often used. They are not limited to direct connection but include connection through other elements where such connection is recognized as being equivalent by those skilled in the art.

DETAILED DESCRIPTION OF EMBODIMENTS

The present invention and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments described in detail in the following description.

System Overview

Generally speaking, tractor mode propulsion of the preferred embodiments includes a fully submerged, fixed shaft drive line in a “pulling” mode.

More specifically, and referring to the FIGS. 1 and 2. the engine of the marine vessel is coupled to a drive by way of a shaft or similar connection, which extends toward the front (bow) of the vessel and which may be accommodated by a “tunnel” or similar structure. The drive shaft is coupled to the drive and configured to rotate about its longitudinal axis for driving the propeller. In particular, the drive shaft extends toward the front of the vessel at a predetermined angle and terminates in the aforementioned tractor propeller, which is configured to pull water rearwardly relative to the bow (i.e., tractor configuration).

The resulting design provides a propeller location closer to the bow than in known systems. As depicted in FIG. 2, the shaft angle is set at about 6 degrees, which gives an effective shaft angle of approximately zero considering the hull's running angle of attack and water flow angle into the propeller due to the tunnel shape of the boat.

The invention delivers a number of advantages over conventional designs such as cavitation-free operation at up to 50 knots and greater with a fully wetted, submerged propeller thereby improving propeller efficiencies. Positive shaft angles also provide the vessel with a natural bow-up tendency, which is particularly advantageous at higher speeds such as during trimming out an outdrive. An interceptor may further be provided in the tunnel to provide adjustable transom lift and bow down as required through manual control or automatic computer control.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Marine propulsion systems are designed for a variety of applications. Beginning with FIG. 1, a tractor-mode marine propulsion configuration of the preferred embodiments is shown on the bottom side of a marine vessel 10. Marine vessel 10 shows twin propellers 12, but the invention may be applied to single-propeller vessels or any number of propellers. Marine vessel 10 includes a hull 44 that forms a bow 24, a transom 26, and chine 22. A rudder 28 allows steering control of vessel 10 and is shown attached to the transom 26. The rudder may, however, be located anywhere on the vessel 10. A tunnel(s) 32 forms a recess in the hull 44 of the marine vessel 10 which houses the propeller 12. The propeller may he located entirely within tunnel 32, or partially within tunnel 32. Preferably, at least half of the diameter of propeller 12 is located within the tunnel. A series of interceptors may be used to control the pitch of the marine vessel 10 as it moves through the water. The interceptors 30 may be automatically extended to create lift, thus providing the captain added control. The amount the interceptors extend from the transom may be automatically controlled or manually configured.

The propeller 12 is driven by a fixed propeller shaft 16. The rotation of the propeller shaft 16 and the blade pitch of the propeller 12 characterize the propulsion system as a tractor mode configuration. In tractor mode, the propeller 12 faces the bow 24 of the vessel, such that water is drawn from the bow 24 of the marine vessel 10 and expelled toward the transom 26 to effectively “pull” the vessel through the water. This is contrary to typical configurations where the propeller is located closer to the transom 26 and “pushes” the vessel 10 through the water. In order to qualify as a tractor mode configuration in the preferred embodiments, the propeller 12 should be located 10%-60% toward the bow 24 from the transom 26. For example, at 50%, the propeller would be at the midpoint of the length of the vessel 10. Preferably, the propeller 12 is located 20% toward the bow 24 from the transom 26.

The propeller 12 is driven by the propeller shaft 16 that is supported by a propeller shaft strut 14. The propeller shaft 16 may pass through the hull 44 with a thru hull 18 port and be exposed to water or may be totally enclosed within the hull 44. In an exposed configuration, as shown in FIG. 1, the thru hull port 18 may also he used as a water intake port for cooling the engine or other water intake needs. Preferably, a sleeve 50 connects to the hull 44 and encapsulates the propeller shaft 16 and prevents any contact of the propeller shaft 16 with water, as best shown in FIG. 3.

As shown in FIGS. 2 and 3, the tractor-mode orientation of the propeller 12 draws water into the tunnel 32 to create a flow and pull of the vessel 10 through the water. An engine 38 within hull 44 may also be located in close proximity to transom 26 and generate rotational force through an output shaft 42. The output shaft 42 redirects the rotational force with a gearbox 40 to the propeller shaft 16 and ultimately to propeller 12. Any known device may be used to redirect the rotational force, such as a u-joint. Preferably, a gearbox 40, such as a v-drive, may be used. While the gearbox 40 is shown within the hull 44, it may be located outside of the hull 44 as well. Either of these configurations locates the engine 38 in close proximity to the transom 26 and creates more usable space within the hull 44. Notably, more traditional drives, such as “pusher” drives, locate the engine 38 farther away from the transom 26 and therefore occupy more space within the hull 44.

Tunnel 32 is preferably formed uniquely for each vessel 10. Different bull 44 designs require different tunnel 32 cross sections in order to perform at optimum levels. In the tunnel design of the preferred embodiment, the flow 34 of water through the tunnel does not create vortexes or turbulence. In other words, water approaching the propeller 12 will have a generally axial flow path, thus increasing the efficiency of the propeller. The inflowing water will also be free of aeration or cavitation, which can otherwise be a problem, especially at speeds of greater than 20 knots. In fact, in the preferred embodiments, problems due to issues like cavitation are dramatically lessened (compared to, for example, known “pusher” drives) at speeds of 50 knots or more. This increases overall efficiency and lowers fuel consumption.

Preferably, the propeller shaft 16 creates an angle of between 3-12 degrees, and preferably about six (6) degrees or less, with the bottom datum line 46 of the vessel 10 when it is not moving. When the vessel 10 is moving through the water, e.g., at a speed of 20-50 knots or more, an effective shaft angle of 0 degrees is produced as the bow 24 pitches upward. The shaft angle is defined as the angle created between bottom datum line 46 and the propeller shaft 16. The effective shaft angle may be defined as the angle of the propeller shaft 16 minus the hull running trim angle and minus the water flow angle into the propeller disc. As the vessel's speed changes, the angle of attack changes and creates a different effective shaft angle.

The interceptors 30 may also be deployed/retracted as shown by arrows 36 to achieve a 0 degree effective shaft angle. Propellers 12 in this configuration are fully wetted and experience high efficiency of up to 80% while producing little or no cavitation. As the propeller shaft 16 and propeller shaft strut 16 are behind the propeller 12, the propeller 12 is fed calm, turbulence-free water which substantially eliminates cavitation.

The hull 44, tunnel 32, and the angle of the propeller shaft 16 all work together to attain an effective 0 degree shaft angle at a cruising running angle of attack. As the speed of a planing hull increases, the trim angle, or angle of attack decreases. The angle of attack is the angle between a reference line on the marine vessel's hull 44 and the vector representing the relative motion between the hull and the water through which it is moving. In sum, angle of attack is the angle between a reference line on the hull 44 and the oncoming water flow. While the angle of attack has an inverse relationship with hull speed, the hull design, weight distribution, and shaft angle determine what exactly the angle of attack will be at a given speed. Despite the relatively predetermined angle of attack, interceptors 30 may be used to dynamically adjust the angle of attack. In order to produce the most amount of thrust with the least amount of energy expended, a 0 degree shaft angle is optimal. As a result, it is possible to achieve an effective shaft angle of 0 degrees when the marine vessel is in motion at a cruising angle of attack due to the novel weight distribution of the engine 38, shaft angle, tunnel design, and overall hull design. An interceptor 30 may be used to fine-tune the angle of attack and maintain a 0 degree shaft angle at cruising speed. Additionally, the propeller's propulsive coefficient, a constant that determines the amount of thrust produced for an amount of input power, may be increased due to the weight distribution of the engine 38. hull design, effective shaft angle and undisturbed water flow into the propeller disc.

Cruising speed is a relative term that changes according to hull design, weight distribution, and shaft angle. Cruising speed for a displacement hull may he defined as the speed in which a particular marine vessel experiences rapidly diminishing returns for the amount of power needed for an increase in speed. It is a function of how far astern the wake is forming and how large of a hole in the water between bow wave and wake the boat has to climb out of lit varies depending on the efficiency of the hull but is somewhere near, in knots, the number found by about one and a third times the square root of the waterline length in feet.

Cruising speed for a planing hull is also related to efficiency but is a bit more dependent on hull bottom shape, engine performance. vibrations, and fuel consumption. As hull bottom design is very relevant once the hull is planing on the water surface, weight distribution of the engine plays a critical role in determining cruising speed.

The rotating propeller 12 creates what is known as a “propeller disc”. The inventive configuration produces a propeller disc which generates thrust on the upper and lower halves of the propeller 12. Some known configurations only generate thrust on the lower portion of the propeller disk, further increasing drive efficiency of the preferred embodiments.

Moving on to FIG. 3, another embodiment of the invention is shown. In this embodiment the engine 38 is shown supported by engine mounts 48. The output shaft 42 transmits rotational force through the gearbox 40 and to the propeller 12 with a propeller shaft 16. The propeller shaft 16 is kept within the hull 44 of the vessel 10 with the use of a sleeve 50. The sleeve may be incorporated with the propeller shaft strut 14 as shown, or may be an extension of the material that the hull 44 is formed with, for example, aluminum or fiberglass. Keeping the propeller shaft 16 within the hull may extend the service life of the drive system as it is shielded from the harsh elements found in the water and also eliminates the drag of a rotating shaft in water. The propeller 12, propeller shaft 16, sleeve 50, and propeller shaft strut 14 may also be manufactured independently and installed in the tunnel 32 of various marine vessels 10.

Although the best mode contemplated by the inventors of carrying out the present invention is disclosed above, practice of the present invention is not limited thereto. It will be manifest that various additions, modifications and rearrangements of the features of the present invention may be made without deviating from the spirit and scope of the underlying inventive concept. 

What is claimed is:
 1. A marine vessel comprising: a hull including a bottom with at least one tunnel configured to accept a drive; wherein the drive includes a fixed shaft and a tractor mode configured propeller mounted at least partially within the tunnel and configured to rotate such that a thrust is created pulling the marine vessel in a forward direction.
 2. The marine vessel of claim 1, wherein the fixed shaft is joined to the propeller with a shaft angle of between 3-12 degrees to a horizontal plane when the marine vessel is stationary in the water, and producing an effective shaft angle of about 0 degrees when the marine vessel is in motion at a cruising running angle of attack.
 3. The marine vessel of claim 2, wherein the shaft angle is about 6 degrees or less to the horizontal plane.
 4. The marine vessel of claim 1, wherein the fixed shaft includes a positive shaft angle producing a lift in a bow region of the marine vessel when moving at cruising speed.
 5. The marine vessel of claim 1, wherein the propeller is fully submerged in water and does not produce a vapor cavity when powering the marine vessel at a speed greater than 20 knots.
 6. The marine vessel of claim 5, wherein the speed is greater than 50 knots.
 7. The marine vessel of claim 1, wherein the propeller includes efficiency ratios of over 60%.
 8. The marine vessel of claim 1, wherein the propeller includes a completely clean inflow condition.
 9. The marine vessel of claim 1, wherein the propeller includes an overall propulsive coefficient of over 50%
 10. The marine vessel of claim 1, further comprising an interceptor on a trailing edge of the tunnel providing the bow of the marine vessel with an adjustable positive and a negative lift when moving at cruising speed.
 11. The marine vessel of claim 1, wherein when cruising at a speed greater than 20 knots, the marine vessel does not produce a roostertail.
 12. The marine vessel of claim 1, further comprising a power source within the hull of the marine vessel mounted rearward of the propeller.
 13. A drive for a marine vessel comprising: a fully wetted propeller when the marine vessel is floating in water; a fixed drive shaft configuring the propeller in a tractor mode wherein the propeller pulls the water rearwardly relative to a bow of the marine vessel when traveling in a forward direction; and wherein the propeller is mounted in a range of 10%-60% of a length of the marine vessel toward the bow from a transom.
 14. The drive for a marine vessel of claim 13, further comprising a tunnel in a bottom of the hull, wherein at least a portion of the propeller is mounted within the tunnel.
 15. The drive for a marine vessel of claim 13, wherein the propeller includes a diameter in the range of about 50% to 90% of a diameter of the tunnel.
 16. The drive for a marine vessel of claim 13, wherein the propeller rotates to produce a thrust disc such that both an upper half and a lower half of the propeller produce the thrust.
 17. The drive for a marine vessel of claim 13, wherein the propeller: produces an effective shaft angle of 0 degrees when the marine vessel is in motion at a cruising running angle of attack; and does not produce cavitation during operation powering the marine vessel at a speed greater than 20 knots.
 18. The drive for a marine vessel of claim 17, wherein the speed is greater than 50 knots.
 19. The drive for a marine vessel of claim 13, further comprising: a v-drive unit within a hull of the marine vessel; and wherein the drive shaft is substantially fully enclosed within the hull of the marine vessel.
 20. The drive for a marine vessel of claim 13, further comprising: an interceptor on a trailing edge of the tunnel providing the bow of the marine vessel with an adjustable positive and a negative lift when moving at cruising speed; and wherein the propeller does not produce a rooster tail when the marine vessel is cruising at a speed greater than 20 knots.
 21. The drive for a marine vessel of claim 13, further comprising: a power source within a hull of the marine vessel and rearward of the propeller; or any position desired in the hull and a v-drive unit within the hull of the marine vessel; and wherein the fixed drive shaft is fully enclosed within the hull of the marine vessel.
 22. The drive for a marine vessel of claim 13, wherein the propeller includes: efficiency ratios of over 60%; and an overall propulsive coefficient of over 50%. 